Electric light



y 6- c. w. DAKE 2,040,243

ELECTRIC LIGHT Filed April 23, 1931 INVENTOR Char105 W. .DaJflb ATTORNEY Patented May k 12,

UNITED STATES PATENT OFFICE ELECTRIC LIGHT Charles W. Dake, ChicagoQIll. Application April 23, 1931, Serial No. 532,255 5 Claims. (Cl. 176-31) This invention relates to an incaniescent filement electric lamp, particularly to one which is theft proof.

L It has for one object to provide in connection with such a lamp automatic means for rendering the lamp removable after the fllament has burned throughout.

Another object of the invention is to provide in a theft proof lamp means whereby the bulb 10" base may be readily screwed into position in a socket and whereby after having been screwed into the socket it cannot be withdrawn until the filament has been destroyed.

Other objects will appear from time to time in the specification and claims.

My invention is illustrated more or less diagrammatically in the accompanying drawing, wherein:-

Figure 1 is a longitudinal cross section through the lamp;

Figure 2 is a transverse cross section taken at line 2-2 of Figure 1;

Figure 3 is a sectional view similar to Figure 2, showing the parts after the lamp is in condition for removal.

Like parts are designated by like characters throughout the specification and drawing.

A is a glass bulb, which may have an integral inwardly extending portion A carrying a stem A.

Filament supporting members B B are positioned on the stem A A filament B is carried by the members B and is fastened at one end to a lead member B and at the other end to a lead member B These members pass through the wall of the extension A and extend upwardly beyond the member A the lead B terminating in a plug which forms a part of the lamp assembly, and the lead B terminating in a laterally bent portion B which is in electrical connection with the members which will be described hereinafter.

- Fastened to the glass bulb or envelope A by any suitable means, such as cement C, or the like, is a shell C which may be outwardly flared at one end as at C where it contacts the glass A. The shell C is provided adjacent its lower edge with one or more outwardly bent lugs or portions Within the shell G is an insulating shell or sleeve C The shell C and the insulating sleeve are perforated as at C to permit a latch to move and to extend therethrough in a manner which will be described below. At its upper. end the shell C is closed by plug C, formed of insulating material. This plug has its upper, outer edge inclined as at C" and is provided with a depression C in its upper face. It may have one or more depressions or cavities C formed in its lower face. A preferably central perforation C" is formed in the plug. At its upper end the perforation C may be restricted 5 or of reduced diameter, as shown in Figure 1. Along its upper edge theshell C may have one or more inwardly projecting lugs C which pro- Ject into and lie within the cavities C and prevent relative turning of the plug C and the 10 shell 0.

D is an outer shell or base which is preferably threaded on a portion of its surface as shown. At its lower edge it terminates in an inwardly d rected flange D which engages the lugs C of 15 the shell C to prevent or limit relative longitudinal movement of the inner and outer shells At its upper end the shell D is provided with an inwardly extending flange D which is inwardly and upwardly bent along the inclined surface C of the plug C. The shell D has preferably adiacent its upper edge an inwardly directed relatively weak and breakable tongue D which pro jects into the cavity C of the plug C and is held therein preferably by a rivet D. D is an inwardly directed projection formed in any suitable manner upon the outer shell D.

E is a supporting member positioned in the plug C. E is a second supporting member which may be longer than the member E. E is a contact member positioned in the upper end of the perforation C" of the plug C. A connection E leads from the contact member E to a resistance E which is supported between the members E and E A second resistance member E connects the lead B with the laterally bent por-. tion B of the lead B The member B is connected to the resistance E by a connection E. E" is a link fastened at one end to the upper end of the lead E and, therefore, in circuit with 40 the resistance E which is also connected to the upper end of the lead B At its other end the link E is joined to a latch member E which is positioned opposite and adapted to be -moved through the perforation C under the influence of a spring E When the lamp is in operation and before the filament has been destroyed,-the parts are held as shown in Figure 2 by a nonconductive holding member E and the outer and inner shells are not locker; together and may have relative movement. The member E is of a materialwhich will be destroyed or weakened under the influence of heat. When a suflicient current passes through the resistance E to heat that member above a predetermined point, the

rotation, that is to say, rotation to screw the' bulb out of the socket, becomes effective for that purpose and the inner and outer shells move toh gether when the lamp is rotated in the direction to screw 'itout of the socket.

. The use and operation of my invention are as follows: I

The lamp of this invention, to be used, is positioned in a socket and while it may be arranged to be seated in the socket in any fashion, in the particularform shown herewith it is screwed into the socket. After it has beenseated in the socket, a certain additional rotation will break the memberD thus destroying the connection between the inner shell C and the outer shell D and permitting relative rotation of the two. Thereafter, rotation of the lamp does not rotate the outer shell D and since it is that shell which engages the socket, the rotation of the lamp is not eilfective to remove the lamp as a whole from the socket and until some means is found for re-connecting the inner and. outer shells, rotation of the lamp itself is without effect on the outer shell D.

When the lampis in use, the resistance E acts as a capacity resistance, limiting the flow of current into the lamp. The resistance furnished by the filament B and that offered by the resistance E are together equal to the resistance oifered by the differential or capacity resistance member Hi.

When the filament is destroyed or in fact when any part of the filament circuit, which includes the filament and the leads B and B beyond their connections with the resistance E is destroyed, all of the current passing through the lamp must pass through the resistance E This resistance being of less capacity than the resistance E is .heated when the entire volume of current passing through the light is carried by it. The added heat of the resistance E is efiective either to fuse, burn or otherwise destroy the retaining member E or else so to weaken that member that the strength of the spring E is sufiicient to break it. When the retaining member E is broken the spring then moves the latch from the position shown in Figure 2 to that shown in Figure 3, and the inner and outer shells are then so locked that rotation of the bulb carrying with shell, will rotate the outer shell and .thus the lamp as a whole may be removed. The lead B is sufflciently flexible to permit its being bent or moved slightly out when'the latch moves from the inoperative to the operative position.

It wfll be realized that whereas I have herewith shown and described a practical operative device, nevertheless many changes might be made in the size, shape, number and disposition of parts without departing from the spirit of my invention and I wish, therefore, that my showing be taken as in a sense diagrammatic.

I claim:

1. In combination in an electric lamp, a bulb, a shell secured to said bulb, a second shell positioned about said first shell, a breakable member joining it the inner them, the shells-adapted to have relativerota- 'tional movement when the breakable member is broken, a latch movably mounted and adapted in one position to lockthe shells against relative ro-' tation, means destructible by heat, normally hold-- ing the latch in inoperative position, a filament within said bulb, a resistance element of greater resistance than that of the filament, and a second resistance element of less resistance whereby when the filament is intact current will flow through the latter, and whereby when the filament is broken, the current will fiow through the last mentioned resistance to heat the same and thereby to destroy the destructible element.

2. In an incandescent filament electric lamp having a lamp globe with a lighting filament therein and an inner base shell attached thereto, and leads for conducting electricity to and from said filament and extending into thesaid base shell; a heat destructible member and an electrical resistance element associated therewith and con-. nected to the opposite leads; a second base shell surrounding the first said base shell and a latch engaging the base shells upon the parting of the heat destructible member.

3. In an incandescent filament electric lamp having a lamp globe with a lighting filament within the globe, leads connected to the lighting filament and extending therefrom; a base shell secured to the said lamp globe and electrically connected to one of the leads by a spring pressed latching mechanism held in unlatched position by a heat destructible member associated with an electrical heating resistance connecting the said leads, whereby electricity flowing in the heating resistance will heat the same and part the heat destructible member and free the latch to engage the base shell attached to the lamp globe to whereby an excessive fiow of electricity in the heated electric resistance will destroy the heat destructible member allowing the latch to move to latched position of the first and second base shells for unscrewing from the lamp socket.

5. In an incandescent filament electric lamp having a lamp globe, inner and outer base members; a spring pressed latch for making engagement of the base members; a lighting filament within the globe and leads extending from the filament; an' electrical resistance connected to each of said leads in. spaced relation to the lighting filament; -a heat destructible member associated with the said resistance for holding the said latch in unlatched position and allowing the latch I 

